Method and system to provide electrical contacts for electrotreating processes

ABSTRACT

Systems and methods to provide electrical contacts to a workpiece to facilitate electrotreating processes, including electroplating and electroetching processes are presented.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/348,758, filed Oct. 26, 2001, entitled “Method and System toProvide Electrical Contacts For Electrotreating Processes” and is acontinuation-in-part of U.S. application Ser. No. 09/760,757 entitled“Method and Apparatus for Electrodeposition of Uniform Film with MinimalEdge Exclusion on Substrate,” filed on Jan. 17, 2001, now U.S. Pat. No.6,610,190 the contents of which are expressly incorporated by referenceherein.

BACKGROUND

1. Field of the Invention

The present invention generally relates to semiconductor integratedcircuit technology and, more particularly, to electrotreating techniquessuch as electroplating and electroetching that are applied to the entireface of a workpiece.

2. Background of the Related Art

Conventional semiconductor devices such as integrated circuits generallyinclude a semiconductor substrate, usually a silicon substrate, and aplurality of sequentially formed dielectric interlayers such as silicondioxide, and conductive paths or interconnects made of conductivematerials. Copper and copper alloys have recently received considerableattention as interconnect materials because of their superiorelectromigration and low resistivity characteristics. The interconnectsare usually formed by filling a conductor such as copper in features orcavities etched into the dielectric interlayers by a metallizationprocess. The preferred method of copper metallization process iselectroplating. In an integrated circuit, multiple levels ofinterconnect networks laterally extend with respect to the substratesurface. Interconnects formed in sequential layers can be electricallyconnected using features such as vias or contacts.

In a typical interconnect fabrication process, first an insulating layeris formed on the semiconductor substrate. Patterning and etchingprocesses are performed to form features such as trenches, pads and viasetc. in the insulating layer. Then, copper is electroplated to fill allthe features. In such electroplating processes the wafer is placed on awafer carrier and a cathodic (−) voltage with respect to an electrode isapplied to the wafer surface while the electrolyte wets both the wafersurface and the electrode. The voltage is typically applied usingcontacts surrounding the circumference of the wafer. The contacts areusually electrically sealed and isolated from the electrolyte by a clampcovering the circumference of the wafer surface. The clamp inhibitscopper deposition on the contacts but it also inhibit copper depositionalong the circumference of the wafer and causes loss of important spaceon the wafer. In the semiconductor industry, this unused or wasted waferarea is called edge exclusion. In the semiconductor integrated circuitindustry, there is always a drive towards reducing edge exclusion on thewafers.

Once the plating is over, a chemical mechanical polishing (CMP) step, anelectroetching (or electropolishing) or etching step, or a combinationof these steps are conducted to remove the excess copper layer or copperoverburden and other conductive layers that are above the top surface ofthe substrate. This process electrically isolates the copper depositedinto various features on the wafer and thus forms the interconnectstructure. The interconnect process is then repeated as many times asthe number of interconnect layers desired.

In the electroetching process both the material to be removed and aconductive electrode are dipped into the electropolishing orelectroetching solution. Typically an anodic (positive) voltage isapplied to the material to be removed with respect to the conductiveelectrode. With the applied voltage, the material is electrochemicallydissolved and removed from the wafer surface.

Whether a CMP process, an etching process or an electroetching processis employed, it is desirable to reduce the copper overburden thicknessthat needs to be removed by these processes. The importance ofovercoming the copper overburden problem is evidenced by technologicaldevelopments directed to the deposition of planar and thin copper layerson the wafer surfaces. Such planar deposition techniques are generallycalled Electrochemical Mechanical Deposition (ECMD). In such planarprocesses, a pad, a mask or a sweeper, which is collectively called aWorkpiece Surface Influencing Device (WSID), can be used during at leasta portion of the electrodeposition or electroetching processes whenthere is physical contact or close proximity, and relative motionbetween the workpiece surface and the WSID.

The edge exclusion problem may be overcome using deposition technologiesthat deposit materials across the full face of wafers. For example, U.S.application Ser. No. 09/735,546 entitled “Method and Apparatus ForMaking Electrical Contact To Wafer Surface for Full-Face Electroplatingor Electropolishing,” filed on Dec. 14, 2000 and commonly owned by theassignee of the present invention, describes in one aspect a techniquefor providing full face electrotreating. It should be noted thatelectrotreating refers to all electrochemical processes, which aresometimes called by different names. Therefore, electrotreatingincludes, for example, electrodeposition or plating, electroetching orelectropolishing, etc. U.S. application Ser. No. 09/760,757 entitled“Method and Apparatus for Electrodeposition of Uniform Film with MinimalEdge Exclusion on Substrate,” filed on Jan. 17, 2001 and commonly ownedby the assignee of the present invention describes in one aspect atechnique for forming conductive layers on a semiconductor wafer surfacewithout losing space on the surface for electrical contacts. Asexemplified in these applications, copper deposition or electroetchingon a wafer surface can be achieved using electrical contacts to contactthe wafer in a slidable manner, i.e. a relative motion is establishedbetween the contacts and the wafer surface during process so thatmaterial is deposited on or removed from the whole workpiece surfaceincluding the areas right under the contacts. While previously describedelectrical contacts are adequate, needed is an improved contactstructure, which provides for even greater consistency than theestablished electrical contacts.

SUMMARY OF THE INVENTION

The presently preferred embodiments described herein include systems andmethods for providing electrical contacts to the surface of a workpiecesuch as a semiconductor wafer to facilitate electrotreating processes,including electroplating and electroetching processes. The presentinvention provides improved contact structures, which provide forgreater consistency than conventional electrical contacts.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features, aspects, and advantages will becomemore apparent from the following detailed description when read inconjunction with the following drawings, wherein:

FIG. 1 is a diagram illustrating a perspective view of an exemplaryelectrotreating system according to a presently preferred embodiment;

FIGS. 2 and 3 are diagrams illustrating a bottom view and a side view,respectively, of the exemplary electrotreating system of FIG. 1including an exemplary pair of electrical contacts;

FIGS. 4A through 4C are diagrams illustrating side views of exemplarycontact members according to a first presently preferred embodiment andaccording to the exemplary electrotreating system of FIGS. 1 through 3;

FIGS. 5A and 5B are diagrams illustrating the interaction of theexemplary contact members of FIGS. 4A through 4C with the workpiece ofFIGS. 1 through 3;

FIGS. 6A through 6C are diagrams illustrating side views of exemplarycontact members according to a second presently preferred embodiment andaccording to the exemplary electrotreating system of FIGS. 1 through 3;

FIGS. 7A through 7B are diagrams illustrating side views of exemplarycontact members according to a third presently preferred embodiment andaccording to the exemplary electrotreating system of FIGS. 1 through 3;

FIGS. 8A through 8B are diagrams illustrating side views of exemplarycontact members according to a fourth presently preferred embodiment andaccording to the exemplary electrotreating system of FIGS. 1 through 3;

FIG. 9A is a diagram illustrating a side view of an exemplary contactmember according to a fifth presently preferred embodiment and accordingto the exemplary electrotreating system of FIGS. 1 through 3;

FIGS. 9B through 9D are diagrams illustrating the interaction of theexemplary contact member of FIGS. 9A with the workpiece of FIGS. 1through 3;

FIGS. 10A and 10B are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system of FIG. 1including an exemplary pair of stationary contacts and a contact membermounting arrangement that includes an enclosure;

FIGS. 11A and 11C are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system of FIG. 1including an exemplary pair of laterally moving contacts and a contactmember mounting arrangement that includes a guide mechanism;

FIG. 11B is a diagram illustrating a detail side view of a portion ofthe mounting arrangement of FIGS. 11A and 11C;

FIG. 11D illustrates an other embodiment of a curved contact member;

FIGS. 12A and 12B are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system of FIG. 1including an exemplary pair of vertically movable contact members and acontact members mounting arrangement; and

FIGS. 13A and 13B are diagrams illustrating embodiments of the presentinvention using back-side contacts.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe accompanying drawings, which are provided as illustrative examplesof preferred embodiments of the present invention.

Referring now to FIG. 1, it is a diagram illustrating a perspective viewof an exemplary electrotreating system 100 according to a presentlypreferred embodiment. FIG. 1 schematically shows an exemplaryelectrotreating system 100 which is capable of performing bothelectroplating and electroetching processes. The exemplaryelectrotreating system of the present invention may be one having thecapability of planar electroplating and planar electroetching such as anElectrochemical Mechanical Deposition (ECMD) or ElectrochemicalMechanical Etching (ECME) system. It should be noted that these systemsare collectively referred to as Electrochemical Mechanical Processing(ECMPR) systems. The exemplary ECMPR system 100 includes an electrode102, a workpiece 104, and a workpiece surface influencing device (WSID)106. The WSID 106 may be, for example, a mask, a mask plate, a pad, asweeper, or other suitable surface influencing device. The WSID 106 maybe over a cavity or a cup 107. A solution 108 fills the cup 107 andtouches the electrode 102 and the work piece 104. If plating is to beperformed, or both plating and electropolishing are to be performed, thesolution 108 will typically contain the ionic species of the metal to bedeposited and additives for good quality film formation. For plating orplating and etching, an exemplary copper plating solution may be, forexample, a copper sulfate solution with additives that are commonly usedin the industry. If only electropolishing is to be performed, however,the solution 108 used may be a typical electroetching/polishingsolution, which does not contain ionic species of the material to beetched. For copper electroetching, solutions containing an acid, such asphosphoric acid are common. The workpiece 104 may be, for example, asilicon wafer to be plated with a conductor metal, preferably copper orcopper alloy. The wafer 104 includes a front surface 109 to be platedwith copper and a bottom surface 110 to be held by a carrier head 111.The carrier head 111 is rotated by a shaft 112 or spindle. The shaft 112is placed through a non-rotating shaft housing 113, which is movablyattached to a support structure (not shown). The shaft housing can besimultaneously moved with the shaft 112 and the carrier head 111 whenthe shaft 112 and the carrier head 111 are moved along the z or xdirections. The WSID 106 includes a top surface 114, a bottom surface115, and channels 118 or openings extending between the top and thebottom surfaces 114, 115. The channels 118 may have any form, size, ormay form any pattern on the WSID 106 for better film uniformity. Anychannel 118 shape that allows fluid communication between the wafer 104and the electrode 102 through the WSID 106 can be used. Although in FIG.1 the WSID 106 has a rectangular shape, it may be shaped in anygeometrical form. In U.S. application Ser. No. 09/960,236 entitled “MaskPlate Design,” filed on Sep. 20, 2001, also assigned to the sameassignee as the present invention, discloses various mask plateembodiments.

As previously mentioned, the exemplary electrotreating system 100 iscapable of performing planar or non-planar electroplating as well asplanar or non-planar electroetching. In this respect, if a non-planarprocess approach is chosen, the front surface 109 of the wafer 104 isbrought into proximity of the top surface 114 of the WSID 106, but itdoes not touch it, so that non-planar metal deposition can be performed.Further, if a planar process approach is chosen, the front surface 109of the wafer 104 contacts the top surface 114 of the WSID 106 in oneaspect of the invention. As the plating solution, depicted by arrows108, is delivered through the channels 118, the wafer 104 is moved whileeither the front surface 109 contacts the top surface 114 or is in closeproximity of the top surface 114 of the WSID 106. The wafer 104 may bemoved rotationally which may be clockwise or counter clockwise, or itcan be moved laterally along the x-axis of the WSID 106, or it can beboth rotated and moved laterally. Under an applied potential between thewafer 104 and the electrode 102, and in the presence of the solution 108that fills the channels 118, the metal such as copper, is plated on oretched off the front surface 109 of the wafer 104. It is noted, however,that the above description described rotation and movement of the wafer104, while assuming that the WSID 106 was stationary. It is understoodthat the system 100, as described above, will allow for either the waferor the WSID to move, or for both of them to move, thereby creating thesame relative motion effect. For ease of description, however, theinvention was above-described and will continue to be described in termsof movement of the wafer.

FIGS. 2 and 3 are diagrams illustrating a bottom view and a side view,respectively, of the exemplary electrotreating system 100 of FIG. 1including an exemplary pair of electrical contacts 116. As shown inFIGS. 2 and 3, during electroplating or electroetching processes,cathodic or anodic potentials can be applied through the electricalcontacts 116 that touch an exposed edge 120 of the front surface 109 ofthe wafer 104 as the wafer 104 is moved, i.e., moved laterally, rotated,or both rotated and moved laterally. The electrical contacts 116 areconnected to a power source terminal (not shown) through electricallines 121. In accordance with the principles of the present invention,electrical contacts 116 may include unidirectional or bi-directionalcontact members. As exemplified in FIGS. 4A through 5B, the contactmembers preferably used for cases when the wafer is rotated either inclockwise direction or counter clockwise direction. However, asexemplified in FIGS. 6A through 9D, there are shown contact memberspreferably used for rotation in both directions. Referring also to FIGS.10A through 12A and as will be described more fully below, theelectrical contacts 116 of the system 100 can also be made stationary,laterally movable and vertically movable.

FIGS. 4A through 4C are diagrams illustrating side views of exemplarycontact members 122A, 122B according to a first presently preferredembodiment and according to the exemplary electrotreating system 100 ofFIGS. 1 through 3. As illustrated in FIGS. 4A and 4B, the contactmembers 122A, 122B include a base 124 and one or more contact elements126. In this embodiment the contact elements 126 are brushes that aremade of bundles of conductive bristles 128 or wires. Bristles 128 may,for example, be made of flexible alloy wires, Pt alloy wires orstainless steel wires or the like. The base 124 may be made of copper,stainless steel, titanium or the like or may be coated as the brushesdescribed below. The brushes 126 are preferably made from, or coatedwith, conductive materials that do not react with the solutions used,and if used for deposition, resist Cu plating. Materials or coatingssuch as platinum, platinum alloys, Ta, TaN, Ti, TiN and the like can beused. These conductive materials and considerations are preferably usedfor the other embodiments described below.

The brush 126 can have a length in the range of 1 to 4 cm, preferably2–3 cm., although any suitable length may be used. The length of thebrush and the distance pushed by the wafer surface against the bristlesdetermine the force that is applied on the wafer surface by the brush126. As a rule of thumb, the longer the brush, the milder the force thatis applied on the wafer, and the lesser the chance of having scratchesalong the exposed edge 120 shown in FIG. 2. Each contact element is madeup of a number of bundles, preferably 5 to 20, and most preferably atleast 10, with each bundle having a number of individual wires, such asbetween 20 to 300, preferably in the range of 50 to 200, if 0.002 inchthick wire is used, but will vary as needed. In this embodiment, becausethe brushes 126 are slanted to the right, the contact member 122A ispreferably used when the wafer 104 is rotated in way that it travels tothe right over the contact elements 126. Similarly, the contact member122B is preferably used when the wafer 104 is moving to the left overthe brushes.

As shown in FIG. 4C, the angle of slant, depicted by ‘A’, for brushes126 in both contact members 122A and 122B is about 45 degrees, so thatthe angle of slant is preferably between 30 to 60 degrees, although anysuitable angle may be used. The angle of slant ‘A’ is the angle measuredbetween an upper surface 130 of the base 124 and a slant axis 132 thatis symmetrically crossing the center of the brush 126. The angle ofslant allows the brushes 126 to flex easily and uniformly as the wafer104 makes contact with the contact members 122A or 122B.

FIGS. 5A and 5B are diagrams illustrating the interaction of theexemplary contact members of FIGS. 4A through 4C with the workpiece 104of FIGS. 1 through 3. In operation, as shown in FIGS. 5A and 5B, as awafer 104 moves from a first position ‘A’ to a second position ‘B’ alonga distance d, the brush 126 is pressed down by the same distance d. Asthe distance d gets longer, the force applied on the wafer 104, as wellas the chance of scratching the wafer 104, increase. However, as theangle “A” gets smaller (FIG. 4C), the force gets lower, and there isless chance of scratching the wafer 104.

FIGS. 6A through 8B illustrate contact members that are preferably foruse irrespective of the direction that the wafer is moved. Rotationaldirection of the wafer can be changed any time during the process. FIGS.6A through 6C are diagrams illustrating side views of exemplary contactmembers 136 according to a second presently preferred embodiment andaccording to the exemplary electrotreating system 100 of FIGS. 1 through3. As shown in FIG. 6A, in one embodiment, the contact member 136includes a series of contact elements 138 that are assembled into a base140, preferably a base frame. In this embodiment, the contact elements138A are rollers. Further, as shown in FIG. 6B, the rollers 138A arepreferably disk shaped with a flat contact surface 139 that enable therollers 138A to roll over the wafer 104 surface while establishingelectrical contact. Because of the flat surface 139 of the rollers 138A,the rollers 138A of the contact member 136 are held in a perpendicularposture on the wafer 104 when the member 136 makes contact to the wafer104. The base frame 140 may have a first frame halve 142 and a secondframe halve 144. The rollers 138A are movably held between the first andthe second halves 142, 144 by pins 146 which are placed through thecenters of the rollers 138A and secured to the halves 142, 144 from bothends of the pins 146.

FIG. 6C shows an alternative roller design, with rollers 138B, having around contact surface 150. Similar to the rollers 138A described above,the rollers 138B are held between the first and second halves 142, 144of the base frame 140 by a number of pins 146. The round contact surface150 of the rollers 138B enables them to contact the wafer 104 surface atan angle. In both designs, the rollers 138A, 138B may be furnished withsuitable mechanical biasing mechanisms to enhance their contact abilitywith the wafer 104 surface. Such biasing mechanisms can be, but notlimited to, springs that are placed adjacent the pins 146 and biasingthe rollers 138A, 138B towards the wafer 104. Such biasing mechanismsmay also assist the rollers 138A, 138B to move smoothly on the surfaceof the wafer 104.

FIGS. 7A through 7B are diagrams illustrating side views of exemplarycontact members 152 according to a third presently preferred embodimentand according to the exemplary electrotreating system 100 of FIGS. 1through 3. FIGS. 7A and 7B show the contact member 152 having a base 154and a contact element 156. In this embodiment the contact element 156 isa loop contact having a loop-shape configuration. The loop contact 156may be attached to the base 154 through a lower portion 158 of thecontact 156. In this embodiment, an upper portion 160 of the contact 156may preferably be made flat. The loop contact makes physical andelectrical contact with the wafer surface through the upper portion 160when it is placed on the wafer. The loop shape of the loop contact 156enhances the contact that occurs during its placement on the wafer bycreating a spring action against the wafer. As shown in FIG. 7B, inanother design, the loop contact 156 may have an upper portion 162 withcurved or convex shape. The loop contact may be made of conductivewires, strips or flat pieces. The base 154 is preferably made of aconductive material. It should be noted that the loops in FIG. 7A or 7Bmay be empty loops, or there may be a compressible material such as afoam material inside the loop to support the upper portion 160 better.

FIGS. 8A through 8B are diagrams illustrating side views of exemplarycontact members 166 according to a fourth presently preferred embodimentand according to the exemplary electrotreating system of FIGS. 1 through3. FIG. 8A shows the contact member 166 having a base 168 and a contactelement 170. The contact element 170 may be a conductive bar attached tothe base 168 by at least a pair of flexible members 172, such as leafsprings. As shown in FIG. 8B in a side view, the bar 170 may have around upper portion 174 allowing the contact member to be placed on thewafer at an angle. The flexible members 172 push the bar 170 against thewafer and thereby enhance electrical contact between the wafer and thecontact member. The base and the flexible members are all preferablymade of conductive materials. It should be noted that the contactelement 170 may be a thin conductive foil such as a 25–1000 micron thickmetallic foil. In this case, to support this thin foil, the flexiblemembers 172 are replaced by a compressible member (not shown) such as afoam material that is placed between the contact element 170 and thebase 168.

FIGS. 9B through 9D are diagrams illustrating the interaction of theexemplary contact member 176 of FIGS. 9A with the workpiece 104 of FIGS.1 through 3. FIGS. 9A through 9D show the contact member 176, which canbe used as a bi-directional contact. As shown in FIG. 9A, the contactmember 176 includes a base 178 and one or more contact elements 180. Inthis embodiment, the contact elements 180 are brushes that are made ofbundles of conductive bristles 182 or wires. Bristles 182 may, forexample, be made of flexible alloywires, such as stainless steel wiresor the like. The base 178 is preferably made of a conductive material.The brush 180 can have a length in the range of 1 to 5 cm., preferably 2to 3 cm., although any suitable length may be used. The length of thebrush 180 determines the force that can be applied on the brush 180. Asa rule of thumb, the longer the brush, the milder the force that isapplied on the wafer 104, and the lesser the chance of having scratchesalong the exposed edge 120 shown in FIG. 2. Each contact member is madeup of a number of bundles, preferably 5 to 20, and most preferably atleast 10, with each bundle having a number of individual wires, such asbetween 20 to 300, preferably in the range of 100 to 200, if 0.002 inchthick wire is used, but will vary as needed. The brushes are preferablyslanted at angles of between 30 and 60 degrees, preferably 45 degrees,as shown in FIGS. 4A and 4B, but could also be are placed perpendicularto an upper surface 184 of the base 178 as shown in FIG. 9A.

As shown in FIGS. 9B through 9D, the contact member 176 can be used witha wafer that is moving in either direction. As shown in FIG. 9B, as thewafer 104, which is rotating in the counter clockwise direction, isapproached and contacted with the brush 180 the brush flexes over theright side. At this point, if the rotational direction of the wafer 104needs to be changed, the wafer is first raised above the brush 180 asshown in FIG. 9C. And, the wafer 104 is rotated in the clockwisedirection while the wafer 104 is approached to the brush 180 so that thebrush can be flexed over the left side.

Referring back to FIGS. 1 through 3, as previously mentioned, the system100 may include stationary, laterally movable, or vertically movableelectrical contact structures. Again, as previously mentioned, each suchelectrical contact structure may include the above described contactmember embodiments.

FIGS. 10A and 10B are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system 100 of FIG.1 including an exemplary pair of stationary contacts 182 and a contactmember mounting arrangement that includes an enclosure 188. Asillustrated in FIGS. 10A and 10B, the stationary contacts 182 can beintegrated with the system 100. The stationary contacts 182 can be anyof the specific contact members described in detail above with regard tothe above described embodiments. An exemplary brace portion 184 of thestationary contact 182 connects the stationary contact 182 to theenclosure 188 that contains the system 100, or it may be simply fixedonto the cup 107 (not shown). It is understood that, in this embodiment,the stationary contacts 182 are stationary with respect to the WSID 106.The stationary contacts 182 can be positioned adjacent the WSID 106. Thestationary contacts 182 may be biased toward the wafer 104 with abiasing mechanism (not shown), such as a spring, to provide bettercontact between the contacts 182 and the wafer 104. FIG. 10B shows theposition of the stationary contacts 182 with respect to the WSID 106 andthe wafer from a partial bottom view. As the wafer 104 is rotated inclockwise or counter clockwise directions as well as laterally moved inthe x-direction, the stationary contacts 182 touch the exposed edge 120of the wafer 104. For clarity of illustration, electrical connections tothe contact elements have not been shown in any of the figures. Commonlyknown means and techniques can be used to provide electrical power tothe contact elements. In this embodiment, the stationary contacts mayhave a predetermined length that is based on the size of the wafer, sizeand shape of the WSID 106 and the amount of the lateral motion of thewafer on the WSID. The length of the stationary contacts should be suchadjusted that the exposed edge 120 is continuously contacted by at leastsome of the stationary contacts. In addition, as illustrated in FIG.10A, the height of the stationary contacts may preferably be above thelevel of any solution directly above the WSID so that the wafer 104touches the contacts and voltage can be applied to the wafer 104 via thecontacts prior to any contact between the wafer 104 and the solutionfrom the cup 107.

FIGS. 11A and 11C are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system 100 of FIG.1 including an exemplary pair of laterally moving contacts 190 and acontact member mounting arrangement which includes a guide mechanism.The laterally moving contacts 190 can be any of the specific contactmembers described in detail above with regard to the above-describedembodiments. FIG. 11B is a diagram illustrating a detailed side view ofa portion of the mounting arrangement of FIGS. 11A and 11C. Asillustrated in FIGS. 11A through 11C, a laterally moving contact 190 canbe integrated with the system 100. A brace portion 192 connects thelaterally moving contact 190 to a guide mechanism 194. As shown in FIG.11B in cross section, the guide mechanism 194 can be a rail thataccommodates an end of the brace portion 192 and allows the end of thebrace portion 192 to move along the rail 194. The lateral motion of thecontact 190 is provided by motion rods 195 that are permanently attachedto the shaft housing 113. The lower end of the rods 195 can be removablyinserted into a hole in the end of the brace 192 when the carrier headis lowered down. As the carrier head 111 moves laterally in thex-direction during the process, the rods 195 move the brace 192 in therail 194 and thereby the contacts 190 are moved along with the waferlaterally. Alternatively, the contacts 190 can be connected to a movingmechanism (not shown) that is controlled by a controller (not shown)that causes the movement of the contacts 190 to correspond to thelateral motion of the carrier head 111. The contacts 190 may be biasedtoward the wafer 104 with a spring (not shown) for better conductivitybetween the contacts 190 and the wafer 104. FIG. 11C shows the positionof the contacts 190 with respect to the WSID 106 and the wafer from apartial bottom view. As the wafer 104 is rotated in clockwise or counterclockwise directions as well as laterally moved in the x-direction, thecontacts 190 continue making contact with the exposed edge 120 of thewafer 104 by moving with the wafer 104. Therefore, they do not have tobe as long as those in the case of stationary contacts of FIG. 10B, andthey do not necessarily be straight. As illustrated by the embodimentillustrated in FIG. 11D that shows contacts 190A, the contacts 190A canhave a curved shape that follows the contour of the wafer edge. As alsoillustrated in FIG. 11B, the height of the stationary contacts canpreferably be above the level of any solution directly above the WSID sothat the wafer 104 touches the contacts and voltage can be applied tothe wafer 104 via the contacts prior to any contact between the wafer104 and the solution from the cup 107.

FIGS. 12A and 12B are diagrams illustrating a side view and a bottomview, respectively, of the exemplary electrotreating system 100 of FIG.1 including an exemplary pair of vertically and laterally movablecontacts 196 and a contact members mounting arrangement. As illustratedin FIGS. 12A and 12B, a vertically movable contact 196 can be integratedwith the system 100. The vertically moving contacts 196 can be any ofthe specific contact members described in detail above with regard tothe above described embodiments. A brace portion 198 of the verticallymovable contact 196 may be attached to the shaft housing 113. Asmentioned above the shaft housing 113 can move vertically with thecarrier head in the z direction as well as laterally in the x direction.As the carrier head 111 moves vertically in the z-direction during theprocess, the contacts 196 keep their position along the exposed edge120. In this embodiment, since the only relative motion between thecontacts 196 and the wafer is rotational, this design allows an operatorto adjust the pressure between the contacts 202 and the wafer to adesired fixed level before the process and consequently keep thepressure at that desired level. Lack of relative lateral motion betweenthe contacts 196 and the wafer 104 reduces mechanical abrasion that maybe caused by the contacts 196 over the exposed edge 120. Alternatively,the contacts 196 can be connected to a moving mechanism (not shown) thatis controlled by a controller (not shown) that causes the movement ofthe contacts 196 to correspond to the vertical motion of the carrierhead 111. The contacts 196 may be biased toward the wafer 104 with aspring (not shown) for better conductivity between the contacts 196 andthe wafer 104. FIG. 12B shows the position of the contacts 196 withrespect to the WSID 106 and the wafer from a partial bottom view. As thewafer 104 is rotated in clockwise or counter clockwise directions aswell as laterally moved in the x-direction, the contacts 196 continuemaking contact with the exposed edge 120 of the wafer 104. In thisembodiment the contacts 196 need to be moved out of the way by amechanism (not shown) during the loading of the wafer 104 on the carrierhead 111. After loading the wafer contacts make physical contact to itssurface and the process is initiated. Similar to the case discussed withrespect to FIGS. 11A and 11C, as the wafer 104 is rotated in clockwiseor counter clockwise directions as, well as laterally moved in thex-direction, the contacts 196 continue making contact with the exposededge 120 of the wafer 104 by moving with the wafer 104. Therefore, theydo not have to be as long as those in the case of stationary contacts ofFIG. 10B, and they do not necessarily be straight. They can have acurved shape that follows the contour of the wafer edge.

FIG. 13A illustrates a side view of the exemplary electrotreating system100 of FIG. 1 including an exemplary back-side contacts 202 and acontact member mounting arrangement associated therewith. As illustratedin FIG. 13A, the back-side contact 202 can be integrated with the system100. The back-side contacts 202 can be any of the specific contactmembers described in detail above with regard to the above describedembodiments. In this embodiment, the wafer 204 will have a conductivelayer 206, typically a seed layer, that extends from the frontside 208,around the bevel portion 210, to the backside 212, so that electricalcontact can be

maintained between the wafer 204 and the back-side contact 202 from theback-side of the wafer. In this embodiment, the contact member thatholds the contacts 202 can be attached. A brace portion 198 of theback-side contact 202 may be attached to the shaft housing 113. Asmentioned above the shaft housing 113 can move vertically with thecarrier head in the z direction as well as laterally in the x direction.As the carrier head 111 moves vertically in the z-direction during theprocess, the contacts 196 keep their position along the exposed backsideedge. In this embodiment, since the only relative motion between thecontacts 202 and the wafer is rotational, this design allows an operatorto adjust the pressure between the contacts and the wafer to a desiredfixed level before the process and consequently keep the pressure atthat desired level. Lack of relative lateral motion between the contacts202 and the wafer 204 reduces mechanical abrasion. Alternatively, thecontacts 202 can be connected to a moving mechanism (not shown) that iscontrolled by a controller (not shown) that controls the vertical motionof the carrier head 111. The contacts 202 may be biased toward the wafer204 with a spring (not shown) for better conductivity between thecontacts 202 and the wafer 204. Alternatively, the contact member andback-side contacts 202 can be disposed within the carrier head 111, suchthat electrical contact is established once the wafer 204 is placed ontothe carrier head 111, as shown by the dotted line in FIG. 13A within thecarrier head 111. It should be noted that contact may also be made rightat the edge (bevel) of the wafer.

FIG. 13B illustrates another embodiment of a system that providesbackside contacts. As illustrated, the WSID 106A has dimensions that arelarger than the wafer in all dimensions, such that the entire wafer isexposed to the WSID 106A and the process solution during processing.

Cleaning of the contacts is also a consideration. In one aspect,conventional contacts are, in many instances coated with Cu, Pt, Pd orother materials to ensure repeatability. In time, however, theydeteriorate due to corrosion and the like. Such corrosion will changeuniformity if the contact is stationery with respect to the wafer, butthe uniformity will average out if the contact moves with respect to thewafer, as it will with the present invention. In another aspect, actualcleaning of the contacts can extend their life and increase theuniformity of the contact. Methods of cleaning include electropolishingduring the processing of a wafer, while electropolishing the wafer,usage of a conditioning wafer after processing some number of wafers,either with our without electropolishing occurring, or removal of thecontacts from the system and cleaning them using conditioning pads,electropolishing, or other conventional cleaning operations.

Although the present invention has been particularly described withreference to the preferred embodiments, it should be readily apparent tothose of ordinary skill in the art that changes and modifications in theform and details may be made without departing from the spirit and scopeof the invention. It is intended that the appended claims include suchchanges and modifications.

1. A system for electrical contact with a wafer having a conductivelayer with an edge surface on a front surface thereof during processingof the wafer, comprising: at least one contact member that establisheselectrical contact with the conductive layer only at the edge surface ofthe wafer, the at least one contact member comprising a base supportmember and at least one contact element coupled to the base supportmember, wherein the at least one contact element maintains continuouselectrical contact with a respective exposed edge of the front surfaceof the workpiece and comprises a brush, the brush including a bundle ofconductive wires that contact the front surface of the workpiece at aslant angle so that the workpiece is uni-directionally rotatable againstthe at least one contact member and the relative movement between the atleast one contact member and wafer during processing of the wafer causethe at least one contact member to electrically contact different partsof the edge surface of the wafer.
 2. The system according to claim 1wherein the contact element includes a plurality of bundles ofconductive wires adapted to each contact the front surface of theworkpiece at the slant angle, thereby ensuring that at least one of theplurality of bundles of wires electrically contacts the front surface ofthe workpiece when lateral movement of the front surface of theworkpiece relative to the contact element occurs.
 3. The systemaccording to claim 1, wherein the conductive wires of the brush permitbending so that the workpiece is vertically movable against the at leastone contact member.
 4. A system for electrical contact with a waferhaving a conductive layer with an edge surface on a front surfacethereof during processing of the wafer, comprising: at least one contactmember that establishes contact with the conductive layer at the edgesurface of the wafer, the at least one contact member comprising a basesupport member and at least one contact element coupled to the basesupport member, wherein the at least one contact element maintainscontinuous electrical contact with a respective exposed edge of thefront surface of the workpiece and comprises a brush, the brushincluding a bundle of conductive wires that contact the front surface ofthe workpiece approximately perpendicularly to the front surface of theworkpiece so that the workpiece is bi-directionally rotatable againstthe at least one contact member and the relative movement between the atleast one contact member and wafer during processing of the wafer causethe at least one contact member to electrically contact different partsof the edge of the wafer.
 5. The system according to claim 4 wherein thecontact element includes a plurality of bundles of conductive wiresadapted to each approximately perpendicularly contact the front surfaceof the workpiece, thereby ensuring that at least one of the plurality ofbundles of wires electrically contacts the front surface of theworkpiece when lateral movement of the front surface of the workpiecerelative to the contact element occurs.
 6. The system according to claim4, wherein the conductive wires of the brush permit bending so that theworkpiece is vertically movable against the at least one contact member.7. A system for electrical contact with a wafer having a conductivelayer with an edge surface on a front surface thereof during processingof the wafer, comprising: at least one contact member that establisheselectrical contact with the conductive layer at the edge surface of thewafer, the at least one contact member comprising a base support memberand at least one contact element coupled to the base support member,wherein the at least one contact element maintains continuous electricalcontact with a respect exposed edge of the front surface of theworkpiece and comprises a roller having a contact surface that contactsthe front surface of the workpiece so that the workpiece is rotatableagainst the at least one contact member and the relative movementbetween the at least one contact member and wafer during processing ofthe wafer cause the at least one contact member to electrically contactdifferent parts of the edge surface of the wafer.
 8. The systemaccording to claim 7, wherein the contact surface of the roller issubstantially flat and contact the front surface of the workpieceapproximately perpendicularly to the front surface of the workpiece sothat the workpiece is bi-directionally rotatable.
 9. The systemaccording to claim 8 wherein the contact element includes a plurality ofrollers each having a flat surface adapted to each approximatelyperpendicularly contact the front surface of the workpiece, therebyensuring that at least one of the plurality of rollers electricallycontacts the front surface of the workpiece when lateral movement of thefront surface of the workpiece relative to the contact element occurs.10. The system according to claim 7 further including a mechanicalbiasing mechanism that is used to bias the roller against the frontsurface of the workpiece.
 11. The system according to claim 10 whereinthe mechanical biasing mechanism is a spring.
 12. The system accordingto claim 7 wherein the contact surface of the roller is rounded andcontacts the front surface of the workpiece so that the workpiece isbi-directionally rotatable.
 13. The system according to claim 12 whereinthe contact element includes a plurality of rollers each having arounded surface adapted to each contact the front surface of theworkpiece, thereby ensuring that at least one of the plurality ofrollers electrically contacts the front surface of the workpiece whenlateral movement of the front surface of the workpiece relative to thecontact element occurs.
 14. The system according to claim 12 furtherincluding a mechanical biasing mechanism that is used to bias the rolleragainst the front surface of the workpiece.
 15. The system according toclaim 14 wherein the mechanical biasing mechanism is a spring.
 16. Thesystem according to claim 14 wherein the roller is configured to contactthe front surface of the workpiece at a slant angle.